Assessment of parasympathetic cardiovascular activity in primary open-angle glaucoma

Purpose To describe the pattern of quantitative parasympathetic cardiovascular autonomic function among patients with normal-tension glaucoma (NTG) and high-tension primary open-angle glaucoma (HTG) patients. Methodology This was cross-sectional study of ninety-two subjects enrolled into three groups: HTG (31 patients), NTG (31 patients) and Control (30 patients). All the participants had anthropometric assessment, ophthalmic examination, baseline cardiovascular examination and the three parasympathetic components of Ewing’s battery of autonomic cardiovascular function tests namely heart rate (HR) response to deep breathing, HR response to Valsalva manoeuvre and HR response to standing. Result The baseline PR intervals were significantly prolonged in HTG (0.18 ± 0.03 s) and NTG (0.18 ± 0.04 s) groups compared with control (0.15 ± 0.03 s) ( p = 0.008). The HTG group had a significantly longer mean RR interval (1.09 ± 0.17 s) than the NTG group (1.03 ± 0.20 s) and control (0.97 ± 0.17 s) during the expiratory phase of the HR response to deep breathing test ( p = 0.037). The HTG group also had significantly longer mean RR intervals around the 15th beat ( p = 0.033) and 30th beats ( p = 0.202) post-standing during the HR response to standing test. The HR response to Valsalva manoeuvre test showed a significantly higher mean Valsalva ratio in the NTG group (1.65 ± 0.48) compared to the HTG group (1.45 ± 0.31) and control (1.43 ± 0.25) ( p = 0.034). Conclusion This study demonstrated that normal-tension and high-tension primary open-angle glaucoma have higher parasympathetic cardiovascular activity than normal individuals.